digraph {
        /* new idea */

        foo [label="whole\ncode"]
        foo -> S1
        allocation -> S1B [label="already\nconnected"]
        interactive -> S1B

        {rank=same; S1 S1B}
        S1 [label="1: know nothing"]
        S1B [label="1: know nothing\n(bound)"]
        S1 -> S1B [label="connect()"]
        S1B -> S1 [label="lose()"]

        S1 -> S2 [label="set_nameplate()"]
        S1B -> P_claim1 [label="set_nameplate()"]
        P_claim1 [shape="box" label="tx claim()"]
        P_claim1 -> S2B

        {rank=same; S2 S2B P_claim2}
        S2 [label="2: know nameplate\nwant claim\nunknown mailbox\nwant open"]
        S2B [label="2: know nameplate\nwant claim\nunknown mailbox\nwant open\n(bound)"]
        S2 -> P_claim2 [label="connect()"]
        S2B -> S2 [label="lose()"]
        P_claim2 [shape="box" label="tx claim()"]
        P_claim2 -> S2B
        S2 -> P2_queue [label="M_send(msg)"]
        P2_queue [shape="box" label="queue"]
        P2_queue -> S2
        S2B -> P2B_queue [label="M_send(msg)"]
        P2B_queue [shape="box" label="queue"]
        P2B_queue -> S2B

        S2 -> S3 [label="(none)" style="invis"]
        S2B -> P_open [label="rx_claimed()"]
        P_open [shape="box" label="store mailbox\ntx open()\ntx add(queued)"]
        P_open -> S3B

        {rank=same; S3 S3B P3_open P3_send}
        S3 [label="3: claimed\nknown mailbox\nwant open"]
        S3B [label="3: claimed\nknown mailbox\nwant open\n(bound)"]
        S3 -> P3_open [label="connect()"]
        S3B -> S3 [label="lose()"]
        /*S3B -> S2 [label="lose()"]*/ /* not worth it */
        P3_open [shape="box" label="tx open()\ntx add(queued)"]
        P3_open -> S3B
        S3B -> S3B [label="rx_claimed()"]
        S3B -> P3_send [label="M_send(msg)"]
        P3_send [shape="box" label="queue\ntx add(msg)"]
        P3_send -> S3B
        S3 -> P3_queue [label="M_send(msg)"]
        P3_queue [shape="box" label="queue"]
        P3_queue -> S3

        S3 -> S4 [label="(none)" style="invis"]
        S3B -> P3_process_ours [label="rx_message(ours)"]
        P3_process_ours [shape="box" label="process message"]
        P3_process_ours -> S3B
        S3B -> P3_process_theirs [label="rx_message(theirs)"]
        P3_process_theirs [shape="box" label="tx release()\nprocess message"]
        P3_process_theirs -> S4B

        {rank=same; S4 P4_release S4B P4_process P4_send P4_queue}
        S4 [label="4: released\nunwant nameplate\nwant mailbox\nopen\n"]

        S4B [label="4: released\nunwant nameplate\nwant mailbox\nopen\n(bound)"]
        S4 -> P4_release [label="connect()"]
        /* it is currently an error to release a nameplate you aren't
        currently claiming, so release() is not idempotent. #118 fixes that */
        P4_release [shape="box" label="tx open()\ntx add(queued)\ntx release()"]
        /*S4B -> S4B [label="rx_claimed() *#118"]*/
        S4B -> P_close [label="M_close()"]
        S4B -> P4_send [label="M_send(msg)"]
        P4_send [shape="box" label="queue\ntx add(msg)"]
        P4_send -> S4B
        S4 -> P4_queue [label="M_send(msg)"]
        P4_queue [shape="box" label="queue"]
        P4_queue -> S4

        P4_release -> S4B
        S4B -> S4 [label="lose()"]
        /*S4B -> S2 [label="lose()"]*/
        S4B -> P4_process [label="rx_message()"]
        P4_process [shape="box" label="process message"]
        P4_process -> S4B

        S4 -> S5 [label="(none)" style="invis"]
        S4B -> S5B [label="rx_released()"]

        seed [label="from Seed?"]
        seed -> S5
        {rank=same; seed S5 S5B P5_open P5_process}
        S5 [label="5: released\nunwant nameplate\nwant mailbox\nopen\n"]
        S5B [label="5: released\nunwant nameplate\nwant mailbox\nopen\n(bound)"]
        S5 -> P5_open [label="connect()"]
        P5_open [shape="box" label="tx open()\ntx add(queued)"]
        P5_open -> S5B
        S5B -> S5 [label="lose()"]
        S5B -> P5_process [label="rx_message()"]
        P5_process [shape="box" label="process message"]
        P5_process -> S5B
        S5B -> P5_send [label="M_send(msg)"]
        P5_send [shape="box" label="queue\ntx add(msg)"]
        P5_send -> S5B
        S5 -> P5_queue [label="M_send(msg)"]
        P5_queue [shape="box" label="queue"]
        P5_queue -> S5

        S5 -> S6 [label="M_close()"]
        S5B -> P_close [label="M_close()"]
        P_close [shape="box" label="tx close()"]
        P_close -> S6B

        {rank=same; S6 P6_close S6B}
        S6 [label="6: closing\nunwant mailbox\nopen\n"]
        S6B [label="6: closing\nunwant mailbox\nopen\n(bound)"]
        S6 -> P6_close [label="connect()"]
        P6_close [shape="box" label="tx close()"]
        P6_close -> S6B
        S6B -> S6 [label="lose()"]
        S6B -> S6B [label="rx_released()"]
        S6B -> S6B [label="M_close()"]
        S6B -> S6B [label="M_send()"]
        S6 -> S6 [label="M_send()"]

        S6 -> S7 [label="(none)" style="invis"]
        S6B -> P7_drop [label="rx_closed()"]
        P7_drop [shape="box" label="C_drop()"]
        P7_drop -> S7B

        {rank=same; S7 S7B}
        S7 [label="7: closed\n"]
        S7B [label="7: closed\n(bound)"]
        S7 -> S7B [label="connect()" style="invis"]
        S7B -> S7 [label="lose()"]
        S7B -> S7B [label="M_close()"]
        S7B -> S7B [label="M_send()"]

}